Sophos is not so bad, but there are better. Why do you limit yourself to Sophos, PestPatrol, and Tiny?
I'm sure if you open up your possibilities a little, you will get a lot of good suggestions here.
McAfee does seem do do well on many of the comparison tests, but it also has a reputation for being a disaster on "some" computers.
I'm a Kaspersky fan and there is KAV Lite for 20 USD if you want good basic protection, without a lot of settings.
NOD is good, F-Secure is good. Lots of possibilities to tailor make your defenses to your individual preferences, setup, etc.
Personally I feel if you don't use Kaspersky, it is also very important to get a good AT such as TDS3, BO Clean or Trojan Hunter.
Look around this forum. There has been a lot of discussion on "whats the best".

This has got little to do with AV, unless you're talking about downloading signatures. In that case there are several scanners that download only very small packages (try Avast for speed of downloading). If scanning speed is important, none beats NOD32.
There are other factors important when it comes to speeding up the internet traffic on your system. For instance try Outpost: it disables ads, caches dns lookups and it helps stopping baddies.